Electronic fuel injection control system

ABSTRACT

An injection valve control signal is generated having a pulse width which is a primary function of sensed intake vacuum, and a secondary function of sensed engine speed, engine temperature, and throttle opening.

United States Patent 11 1 111 3,858,561

Aono 1 Jan. 7, 1975 1 ELECTRONIC FUEL INJECTION CONTROL 3,623,459 11/1971 00111011 .1 123/32 EA SYSTEM 3,689,753 9/1972 Williams 123/32 EA 3,696,303 11/1972 Hartig 123/148 E Inventor: $111299 Aonu, y pan 3,780,587 12/1973 Rivere 123/32 EA [731 Assigneez Nissan Motor p y Limited, 3,780,711 12/1973 Lmdberg 123/32 EA Yokohama City, Japan 1 1 Filed? P 1 1973 Primary Examiner-Charles .1. Myhre [21] APP] NuZ 399,363 Assistant ExaminerCort Flint [30] Foreign Application Priority Data Sept. 22, 1972 Japan 47-94595 152] u.s.c1. ..123/32 EA, 123/119 R 1511 Int. Cl. F02m s1/00,'1=02 1 5/02 A11 111199119n valve 9991191812991 is generated havmg a [581 Field 111 Search 123/32'EA, 119 R Pulse width which is a P y function of sensed take vacuum, and a secondary function of sensed en- 5 References Cited gine speed, engine temperature, and throttle opening.

UNITED STATES PATENTS 3,612,013 10/1971 Gambill 123/32 EA 5 Claims, 11 Drawing Figures INTAKE 370 PRlMARYlCFl VACUUM PULSE SENSOR GENERATOR ENGINE 371 312 TEMPERATLRE CONDARIY s R sE SEN O 372 g 369 (CS) PULSE 302 373 y GENERATOR ENGINE l ARIABLE --\1-ZREQUENCY GENERATOR v DIVIDER 1340 551 566 l- I TIMING ENCODER 511111111 367 13 OUTPUT SLOPE s E egv g SELECTOR SYNCHRONIZING flEMl' l Lili- El lfiE FROM 1 313 94 i gsggfl -g GENERATOR 315 SENSOR SHBLFJELOFF 1 305 6515111111 B Patented Jan. 7, 1975 3,858,561

9 Sheets-Sheet 1 APPROXIMATION OPTIMUM FUEL INJECTiON DURATiON INTAKE VACUUM (F) mm Patented Jan. 7, 1915 3,858,561

9 Sheets-Sheet :5

Fig. 30

300 A INTAKE 370 PR|MARY(CP) vAcUUM PULSE SENSOR GENERATOR 10 5|O 34| ENGINE 3l2 TEMPERATURE 1 372 Q 369 555285??- 502 373 GENERATOR ENGINE sPEEO sENsOR 350 352 CLOCK VARIABLE PULSE FREQUENCY GENERATOR DIVI OER T I I\/+I N G I ENOOOER cIRcUIT 567 T OUTPUT SLOPE AO O E L E R RTION SELECTOR SYNCHRONIZING ilEQfi OR 1 sIGNAL FROM A 3'3 ENGINE FIRST T 504 THROTTLE OPENNG GENERATOR 3|5 SENSOR FUEL & sIIUT-OFF 505 sIGNAL GENERATOR Patented Jan. 7, 1975 9 Sheets-Sheet 6 P- PULSE GENERATOR TRIGGER PuLsE P ARY ANALOG SI AL 370 POTENTIAL T JUNCTION 2 PRIMARY PULSE SIGNAL Patented Jan. 7, 1975 3,858,561

9 Sheets-Sheet '7 Fig. 8

A A STABLE MULTI VIVRATOR DIFFERENTIATING POWER SOURCE FIRST ACCELERA- 'TION SIGNAL SECOND ACCELERA- TlON SIGNAL 575 L w E m H J SECOND ACCELERATION SIGNAL GENERATOR 5 I 4 Patented Jan. 7, 1975 3,858,561

9 Shets-Sheet 8 Fig. 9

THROTTLE VELOCITY SIGNAL SCHMITT TRIGGER OUTPUT FIRST'ACCELERATION T HE SIGNAL 374 INJECTION VALVE H OPENING CYLINDERS 1&3

INJECTION VALVE H F OPENING CYLINDERS 4 a2 9 (g I N SECOND ACCELERATION SIGNAL 373 9(h) INJECTIONVALVE4,,2,| 3,4.2.I,3,4,2,I,3 4 OPENING FIRING ORDER- I34-2 ELECTRONIC FUEL INJECTION CONTROL SYSTEM The present invention relates to an electronic fuel injection control system for an engine which may be employed in a motor vehicle such as an automobile.

Many prior art attempts have been made to optimally 'control fuel injection in response to sensed engine operating parameters, but have proven unsatisfactory. A common drawback in prior art electronic fuel injection control systems is that they are based on an analog design, and are therefore subject to inaccuracies resulting from changes in component performance due to variations in ambient conditions.

It is therefore an object of the invention to provide an electronic fuel injection control system for an engine which is reliable and accurate in performance and overcomes the drawbacks of the prior art.

. This and other objects, advantages and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a graph illustrating a basic design principle of the invention;

FIG. 2 is a simplified block diagram of the invention;

FIG. 3 is a detailed block diagram of a preferred embodiment of the invention;

FIG. 4 is a timing chart for the embodiment of FIG.

FIG. 5 is a schematic diagram of an example of an intake vacuum sensor according to the invention;

FIG. 6 is a schematic diagram of a pulse generator according to the invention;

FIG. 7 is a graph showing the performance of the pulse generator of FIG. 6;

FIG. 8 is a schematic diagram of acceleration signal generators shown in FIG. 3.

FIG. 9 is a timing chart illustrating signals generated by the acceleration signal generators shown in FIG. 8; and

FIG. 10 is a block diagram of a fuel shut-off system shown in FIG. 3.

An engine to which the invention is directed has a fuel injection pump which supplies fuel under a predetermined constant pressure to a fuel injection valve. The amount of fuel injected into the engine is thus proportional to the length of time the fuel injection valve is open. It has been determined experimentally that the optimum duration for fuel injection is a primary function of engine intake vacuum (sensed, for example, at the intake manifold), and a secondary function of other engine operating parameters.

Referring to FIG. 1, optimum fuel injection duration T is shown as a function of intake vacuum P for a typical engine. As is seen, the optimum fuel injection duration T lies within a range between solid lines D and E, since it is a function of other parameters in addition to intake vacuum P. The optimum fuel injection duration T can be approximated as a function of intake vacuum alone by broken lines A and B which intersect at a point C as shown. The slope of the line A is steeper than that of the line B.

FIG. 2 shows the overall configuration of the invention. Intake vacuum, the primary parameter, and secondary parameters such as engine speed, engine temperature, and throttle velocity are sensed as will be described below. An electric primary analog signal 370 having a voltage proportional to the intake vacuum is fed into a primary or P-pulse generator 311. Electric analog signals, an engine temperature signal 371, engine speed signal 372 and-throttle velocity signal 373, proportional to the respective parameters, are fed into a functional adder'310. The P-pulse generator 311 produces an electric primary pulse signal 376 having a pulse width analogous to the voltage of the signal 370. The adder 310 produces an electric secondary analog signal 369 which has a voltage analogous to the sum of predetermined functions of the signals 371, 372 and 373. The signal 369 isfed into a secondary or S-p'ulse generator 312, which in turn produces an electric secondary pulse signal 377. The signals 376 and 377 are then fed into an electronic computing circuit (not designated) which controls an injection pulse generator (not designated) to generate an injection pulse signal 330 having a duration which is a predetermined function of the signals 376 and 377. Generation of the signal 330begins when a synchronizing signal 384 is received from an engine unit such as a distributor, in order to initiate fuel injection at a proper timing in the engine operating cycle. Thus, the timing and duration of fuel injection are optimally controlled by an electronic fuel injection control system embodying the invention.

FIG. 3 shows theFIG. 2 embodiment of the invention in more detail. An intake vacuum sensor 300 senses the engine intake vacuum such as at the intake manifold, and feeds the signal 370into the P-pulse generator 311. An engine temperature sensor 30l, engine speed sensor 302 and a throttle opening sensor 303 suitably sense the respective parameters and feed the signals 371, 372 and 373 respectively into the functional adder 310. A detailed explanation of the signal 373will follow. The adder 310 generates the signal-369, which is the sum of selected functions of the voltages of the signals 371, 372 and 373, and feeds it into the S-pulse generator 312. These selected functions are dependent on individual engine design, must be determined experimentally, and a detailed discussion thereof will be omit: ted for the sake of simplicity.

A clock pulse generator 350 generates mode control pulses 340, which are fed into a timing control circuit 351. The circuit 351 then generates at its output trigger pulses 341 and 342, a clear signal 343, P-latch and S- latch signals 345 and 346, and encoder control pulses 391 and 392 respectively which will be described in detail below. Referring also to FIG. 4, which is a timing chart of important electric signals, the signals 341 and 342 are alternately fed into the generators 311 and 312 respectively, which generate a primary pulse signal 376 and a secondary pulse signal 377 upon receipt of the signals 341 and 342. The signals 376 and 377 have pulse widths analogous to the voltages of the signals 370 and 369 and are respectively fed into an OR gate 353. The generator 350 also generates constant frequency clock pulses 378 which are fed into an operational multiplier or variable frequency divider 352. Variable frequency count pulses 379 are fed from the divider 352 into an AND gate 354, into which an output signal 325 of the gate 353 is also fed.

When outputs from the gate 353 and the divider 352 are simultaneously received at the inputs of the gate 354, an output 380 will be fed into a counter 355 which will count the count pulses 379 from the divider 352 for the duration of the signals 376 and 377. During a P- pulses 379 will be counted for the duration of thesignal 376, and the total count will be transferred to a P-latch 356. During an S-mode period of the signal 340, the count pulses 379 will be counted for the duration of the signal 377, and-the total count willbe transferred to an S-latch 358 through an encoder 390. The operation, as shown in FIG. 4, is carried out under the control of the encoder control pulses 391 and 302 fed into the encoder 390 and an encoder 366 respectively. Thus, it will be understood that the total count of the counter 355 for the duration of the signal 376 is equal to the pulse width of the signal 376 multiplied by the frequency of the count-pulses 379, and analogous to the sensed intake vacuum multiplied by a selected factor. An output 381 of thecounter 355 is fed into a slope selector 367, which senses the value of the output 381 (analogous to the intake vacuum) during the P-mode period. The selector 367 feeds a signal (not designated) into the encoder 366 which has a predetermined value if the intake vacuum is higher than, for example 100 mmI-Ig (corresponding to 3.5 'ms fuel injection duration), and another predetermined value if the vacuum is lower than 100 mmHg. I

Referring back to FIG; 1, the exemplary intake vacuum value of 100 mmI-Ig corresponds to the pointC, and A and B are straight lines. Thus, the optimum fuel injection duration T, as represented by the lines A and B, can be expressed as T= K,P for P s 100 mmI-lg and 1 into divider 352 to control the frequency division ratio thereof. The outputs of the selector 367 and encoder 366'are arranged that in response to the sensed level of the output 381 from the counter 355 by the selector 367, the frequency of the count pulses 379 is K, or K for heavy load operation (the line A) and light load operation (the line B) respectively, in accordance with equations l) and (2). Although FIG. l shows the optimum fuel injection duration T as being approximated by the two straight lines A and B,'it may be approximated by three or more straight lines or a curve within the scope of the invention. A similar operation takes place during the C-mode period, except that if desired,

' t the divider 352 may be controlled by the encoder 366 jinresponse to the pulse 392 to generate the count pulses 379 at-a constant frequency during the S-mode period independent of the value of P. Thus, it will be seen that the generator 350, divider 352, AND gate 354, counter 355, selector 367, and encoder 366 constitute a pulse train generator (no 'numeral)'responsive to the primary and secondary pulse signals 376 and 377 respectively, operative to alternately generate primary and secondary pulsetrain signals (no numerals) respectively, the primary pulse train signal having a first number of pulses (no numeral) which is a first predetermined function of the pulse width of the primary pulse signal 376, and the secondary pulse train signal having a second number of pulses (no numeral) which is a second predetermined function of the pulse width of the secondary pulse signal 377, the primary and secondary pulse train signals being stored in the latches 356 and 358 respectively.

An output (no numeral) of the P-latch 356 is fedinto a decremental counter 357, which initially attains a count equal to the first number of pulse, and thereafter counts downward to zero in response to clock pulses 382 fed thereinto from a variable frequency divider 359, which is similar to the divider 352. Pulses (no numeral) from a real time clock 344 are fed into the divider 359 to produce the pulses 382. An output'(no numeral) of the S-latch 358 is also fed into the divider 359. The frequency division ratio of the divider 359 is controlled in'a manner similar to that of the divider 352, such that the frequency of the clock pulses 382 is a third predetermined function of the second number of pulses. The real time clock 344 and the divider 359 thus constitute a variable clock pulse generator (no numeral) responsive to the secondary pulse trainsignal to generate the clock pulses 382 at a frequency which is the third predetermined function of the second number of pulses.

The synchronizing signal-384 from theengine is fed into the counter 35 7 and also into a flip-flop 360. A count signal 383 is fed from the counter 357 into the flip-flop 360. The counter 357,-initializedto the first numberof pulses, begins to count downward to zero upon receipt of the signal 384, and the counting speed is determined by the frequency of the clock pulses 382. The signal 384 also sets the flip-flop 360 to a high logic level (not designated). The count signal 383 is generated as long as the counting operation'of the counter 357 is being performed, and is terminated when the content of the counter357 reaches zero. At this. time, termination of the signal 383 causes the flip-flop 360 to be reset to a low logic level (not desiganted). Thus, an output signal 331 of the flip-flop 360 fed into 'an OR gate 362 is logically high for the duration of the counting operation of the counter 357.

Thus, the flip-flop 360 acts as the injection pulse generator described in reference to FIG. 2. I It will be seen that the length of time required'for the counting operation of the counter 357 is equal to the initial content multiplied by the frequency of count pulses 382. The counter 357 is thus responsive to the synchronizing signal 384, the primary pulse train signal and the clock pulses 382, and is operative to count the first number of pulses at the frequency of the clock pulses 382. In this manner, a duration J of the high logic level output signal 331 of the flip-flop 360 (injection pulse generator) is latches 356 and 358 are inhibited in order to retain their contents while the counting operation of the counter 357 is being performed.

It will be noticed that the pulse train generator, variable clock pulse generator and counter of FIG. 3 constitute the electronic computing circuit of FIG. 2.

The invention may also include an acceleration compensation system to enrich the air-fuel mixture during acceleration, which includes a power source (not shown), the throttle opening sensor 303, first and second acceleration signal generators 313 and 314 respectively, and the OR gate 362. The generators 313 and 314 are shown in FIG. 8, and a timing chart thereof is presented in FIG..9. The generators shown in FIG. 8 are exemplary, and all components are connected as shown. The sensor 303 (FIG. 3) may be a potentiometer, piezo-electric element, or any other device which produces a voltage proportional to the position of the engine throttle valve. The output of the sensor 303 is a throttle position signal 304, which is applied in parallel to the inputs of the first and second acceleration signal generators 313 and 314. A capacitor C and a resistor R of the generator 313 constitute a differentiating circuit (no numeral). A circuit comprising transistors and O is a Schmitt trigger, and a circuit comprising transistors Q Q and O is an astable multivibrator (no numerals). In operation, the throttle position signal 304 (FIG. 7(a)) is differentiated by the differentiating circuit to produce a throttle velocity signal (FIG. 7(b)), which is indicative of an operators demand to accelerate his engine. If the voltage of the throttle velocity signal is above a threshold. level L (FIG. 7(b)) of the Schmitt trigger, the Schmitt trigger will produce an output as shown in FIG. 7(c). If this output is received by the astable multivibrator, it will generate a first acceleration signal 374 (FIG. 7(d)) which is consequently fed into the OR gate 362. Thus, the gate 362 will produce an output signal 332 in response to at least one of the signal 331 from the flip-flop 360 and the signal 374.

The output of the Schmitt trigger is also applied to a base of a transistor Q of the second acceleration signal generator 314, the emitter of which is connected through a resistor R to a capacitor C In operation, if the Schmitt trigger produces an output, the capacitor C begins to charge, and if the Schmitt trigger output is interrupted, the capacitor C begins to discharge. In this manner, an output is produced by the generator 314 which is the second acceleration signal 373 shown in FIG. 7(g), which is fed to the adder 310. (FIGS. 7(a) and 70) show the effects of the signals 373 and 374 on the signal 331. Unhatched pulses represent the output signal 331 of the flip-flop 360, and hatched pulses are those of the signal 374 which are not coincident with the flip-flop 360 output signal 331. As is clearly seen, the fuel injection duration J is properly increased during engine acceleration.

If desired, the invention may further comprise a fuel shut-off system to inhibit fuel injection during deceleration to reduce the levels of pollutive substances emitted from the engine. An example is shown in FIGS. 3 and 10, which comprises a fuel cut-off signal generator 315, a NOTgate 361 and an AND gate 363. The signal 304 from the throttle opening sensor 303 is fed in parallel into a closed throttle sensor 320 and a differentiator 321 of the generator 315, outputs of which are connected to inputs of an OR gate 324. The sensor 320 generates an output signal when the engine throttle is fully closed, and the differentiator 321 differentiates the signal 304 to obtain the throttle velocity, and produces an output signal if the throttle IS being moved toward a closed position at a velocity greater than a certain value.

The OR gate 324 thus produces an output signal in response to at least one of these conditions, which is fed into an AND gate 323. The signal 373 from the engine speed sensor 302 is fed into an engine speed level detector 322, which feeds an output signal into the AND gate 323 if the sensed engine speed is above a selected value. The AND gate 323 thus produces an output signal if the engine speed is above the selected level and the throttle is closed or being closed rapidly. The output of the AND gate 323 is inverted by a NOT gate 361 to produce a fuel shut-off signal 375 which is fed into the AND gate 363. The gate 363 thus produces the injection pulse signal 330 if the signal 332 is present and the signal 375 is not present. If desired, the detector 322 may have a hystersis characteristic as known in the art and shown in FIG. 10.

A preferred example of the intake vacuum sensor 300 is shown in FIG. 5, in which resistors 333 to 336 and a differential amplifier 337 are connected to the power sourceas shown. The resistors 333 to 336are connected in a bridge arrangement such that the resistors 334 and 335 are of equal value, and a potential difference is produced across leads 338 and 339 proportional to the difference in the values of the resistors 333 and 336, as is well known in the art. The resistor 333 may be piezo-electric may comprise an intake vacuum actuated diaphragm connected to a potentiometer, or may comprise any other means which has a resistance value which varies in proportion to pressure. The output of the differential amplifier 337 is the signal 370 described in detail above.

FIGS. 6 and 7 show the configuration and operation of a preferred example of the generators 311 and 312, in which the P-pulse generator 311 only is shown for simplicity. Transistors Q Q and Q and other circuit components are connected to the power source as shown. In operation, the primary analog signal 370 is continuously received, and if the trigger pulse 341 is not being received, the transistor Q, is turned off (nonconducting), and the transistors Q and O are turned on. Thus, the level of the primary pulse signal 376 which is the output of the generator 311 is substantially zero. When the trigger pulse 341 is received, the potential at the base of the transistor 0;, (or a junction 326) drops in proportion to the level of the signal 370. In response, a constant current is caused to flow through the transistor 0 the capacitor C and the transistor Q (the transistor O is adapted to provide constant cur rent flow therethrough), and the transistor 0 is therefore turned on and the transistor 0 turned off. The level of the signal 376 is thus high, as shown in FIG. 7. The capacitor C charges until the potential at the junction 326 rises to zero, as shown in FIG. 7, at which time the level of the signal 376 drops again to substantially zero. Inthis way, the primary pulse signal 376 is generated in response to the trigger pulse 341 and primary analog signal 370 which has pulses having widths analogous to the voltage level of the primary analog signal 370.

What is claimed is:

1. An electronic fuel injection control system'for an engine, the engine having a fuel injection valve and a synchronizing signal generator to generate an electric synchronizing signal, said control system comprising;

a first sensor to sense a primary operating parameter of the engine and generate an electric primary analog signal analogous thereto;

a second sensor to sense at least one secondary operating parameter of the engineand generate an electric secondary analog signal analogous thereto;

a primary pulse generator responsive to said primary analog signal to generate an electric primary pulse signal having a pulse width analogous thereto;

a secondary pulse generator responsive to said secondary analog signal to generate an electric secondary pulse signal having a pulse width analogous .thereto;

a pulse train generator responsive to said primary and secondary pulse signals being operative to alternately generate primary and secondary pulse train signals respectively, said primary pulse train signal having a first number of pulses which is a first predetermined function of the pulse width of said primary pulse signal, and said secondary pulse train signal having a second number of pulses which is a second predetermined function of the pulse width of said secondary pulse signal;

a variable clock pulse generator responsive to said secondary pulse train signal to generate clock pulses at a frequency which is a third predetermined function of said second number of pulses;

a counter responsive to the synchronizing signal, said primary pulse train signal, and said clock pulses, being operative to count said first number of pulses at the frequency of said clock pulses, the counting operation commencing when said synchronizing signal is received;

and an injection pulse generator connected to said counter and operative to generate an injection pulse signal to open the fuel injection valve for the duration of the counting operation of said counter.

2. A control system as claimed in claim 1, in which said primary operating parameter is the engine intake vacuum,

3. A control system as claimed in claim 2, in which the engine further has a throttle valve, and in which said at least one secondary operating parameter is at least one of the engine temperature, the engine speed and the velocity of the throttle valve. v

4. A control system as claimed in claim 3, which further comprises an acceleration compensation system being operative to lengthen the pulse width of said injection pulse signal in response to an acceleration demand condition of the engine.

5. A control system as claimed in claim 4, which further comprises a fuel shut-off system operative to inhibit generation of said injection pulse signal in regine. 

1. An electronic fuel injection control system for an engine, the engine having a fuel injection valve and a synchronizing signal generator to generate an electric synchronizing signal, said control system comprising; a first sensor to sense a primary operating parameter of the engine and generate an electric primary analog signal analogous thereto; a second sensor to sense at least one secondary operating parameter of the engine and generate an electric secondary analog signal analogous thereto; a primary pulse generator responsive to said primary analog signal to generate an electric primary pulse signal having a pulse width analogous thereto; a secondary pulse generator responsive to said secondary analog signal to generate an electric secondary pulse signal having a pulse width analogous thereto; a pulse train generator responsive to said primary and secondary pulse signals being operative to alternately generate primary and secondary pulse train signals respectively, said primary pulse train signal having a first number of pulses which is a first predetermined function of the pulse width of said primary pulse signal, and said secondary pulse train signal having a second number of pulses which is a second predetermined function of the pulse width of said secondary pulse signal; a variable clock pulse generator responsive to said secondary pulse train signal to generate clock pulses at a frequency which is a third predetermined function of said second number of pulses; a counter responsive to the synchronizing signal, said primary pulse train signal, and said clock pulses, being operative to count said first number of pulses at the frequency of said clock pulses, the counting operation commencing when said synchronizing signal is received; and an injection pulse generator connected to said counter and operative to generate an injection pulse signal to open the fuel injection valve for the duration of the counting operation of said counter.
 2. A control system as claimed in claim 1, in which said primary operating parameter is the engine intake vacuum.
 3. A control system as claimed in claim 2, in which the engine further has a throttle valve, and in which said at least one secondary operating parameter is at least one of the engine temperature, the engine speed and the velocity of the throttle valve.
 4. A control system as claimed in clAim 3, which further comprises an acceleration compensation system being operative to lengthen the pulse width of said injection pulse signal in response to an acceleration demand condition of the engine.
 5. A control system as claimed in claim 4, which further comprises a fuel shut-off system operative to inhibit generation of said injection pulse signal in response to a sensed deceleration condition of the engine. 